Not just hospitals, loads of routes were extended on Sundays to cover for other routes too
In the 90s, the 9, Mortlake-Aldwych/Liverpool Street was a strange one,, it was split when the Hammersmith Bridge had weight restrictions imposed, 9A[Mortlake-Kensington] introduced to cover Mortlake section now 209, 9A had midibuses introduced, [as did every other route over Hammersmith Bridge], but Sundays the 9 operated Aldwych-Mortlake but because of that weight restrictions, the 9 had midibuses allocated, totally unsuitable for such a busy route.